<html dir="LTR" xmlns="http://www.w3.org/1999/xhtml" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:MSHelp="http://msdn.microsoft.com/mshelp" xmlns:tool="http://www.microsoft.com/tooltip" xmlns:ndoc="urn:ndoc-preprocess">
  <head>
    <meta http-equiv="Content-Type" content="text/html; charset=Windows-1252" />
    <title>TYPES</title>
    <link rel="stylesheet" type="text/css" href="ndoc.css" />
  </head>
  <body>
    <div id="header">
      <table width="100%" id="topTable">
        <tr id="headerTableRow1">
          <td align="left">
            <span id="runningHeaderText">VACUUM</span>&nbsp;</td>
        </tr>
        <tr id="headerTableRow2">
          <td align="left">
            <span id="nsrTitle">SQLite Language Reference Documentation</span>
          </td>
        </tr>
        <tr id="headerTableRow3" style="display:none">
          <td>
            <a id="seeAlsoSectionLink" href="#seeAlsoToggle" onclick="OpenSection(seeAlsoToggle)">See Also</a>
            <a id="exampleSectionLink" href="#codeExampleToggle" onclick="OpenSection(codeExampleToggle)">Example</a>
          </td>
        </tr>
     </table>
      <table width="100%" id="bottomTable" cellspacing="0" cellpadding="0" style="display:none">
        <tr>
          <td>
            <span onclick="ExpandCollapseAll(toggleAllImage)" style="cursor:default;" onkeypress="ExpandCollapseAll_CheckKey(toggleAllImage)" tabindex="0">
              <img ID="toggleAllImage" class="toggleAll" src="collall.gif" />
              <label id="collapseAllLabel" for="toggleAllImage" style="display: none;">
							Collapse All
						</label>
              <label id="expandAllLabel" for="toggleAllImage" style="display: none;">
							Expand All
						</label>
            </span>
          </td>
        </tr>
      </table>
    </div>
    <div id="mainSection">
    <div id="mainBody">
      <h1 class="heading">
        SQL As Understood By SQLite</h1>
      <h4>
        VACUUM</h4>
      <p>
        <table cellpadding="10">
          <tr>
            <td align="right" width="1%" nowrap>
              <i><font color="#ff3434">sql-statement</font></i> ::=</td>
            <td>
              <b><font color="#2c2cf0">VACUUM </font></b>[<b><font color="#2c2cf0"></font></b><i><font
                color="#ff3434">index-or-tablename</font></i>]</td>
          </tr>
        </table>
      </p>
      <p>
        The VACUUM command is an SQLite extension modeled after a similar command found
        in PostgreSQL. If VACUUM is invoked with the name of a table or index then it is
        suppose to clean up the named table or index. In version 1.0 of SQLite, the VACUUM
        command would invoke <b>gdbm_reorganize()</b> to clean up the backend database file.</p>
      <p>
        VACUUM became a no-op when the GDBM backend was removed from SQLITE in version 2.0.0.
        VACUUM was reimplemented in version 2.8.1. The index or table name argument is now
        ignored.
      </p>
      <p>
        When an object (table, index, or trigger) is dropped from the database, it leaves
        behind empty space. This makes the database file larger than it needs to be, but
        can speed up inserts. In time inserts and deletes can leave the database file structure
        fragmented, which slows down disk access to the database contents. The VACUUM command
        cleans the main database by copying its contents to a temporary database file and
        reloading the original database file from the copy. This eliminates free pages,
        aligns table data to be contiguous, and otherwise cleans up the database file structure.
        It is not possible to perform the same process on an attached database file.</p>
      <p>
        This command will fail if there is an active transaction. This command has no effect
        on an in-memory database.</p>
      <p>
        As of SQLite version 3.1, an alternative to using the VACUUM command is auto-vacuum
        mode, enabled using the <a href="pragma.html#pragma_auto_vacuum">auto_vacuum pragma</a>.</p>
      <p>
        &nbsp;</p>
      <hr>
      <div id="footer">
        <p>
          &nbsp;</p>
        <p>
        </p>
      </div>
    </div>
    </div>
  </body>
</html>
